Pressure carburetor



May-l2, 1942. s, MQUDALE PRESSURE CARBURETOR Filed June 24, 1940 3 Sheets-Sheet l 3 Sheets-Sheet 2 s. M. UDALE PRESSURE CARBURETOR Filed June 24,- 1940 y- .s. M. UDALE 2,283,021

PRESSURE CARBURETQR Filed June 24, 1940 4 5 Sheets-Sheet 3 I: I 5) I i l f 1 l .J v

Patented May 12, 1942 I I OFF-ICE;

rnsssoan CARBURETOR Stanley M. Udale, Detroit, Mich, assignor to George M. Holley and Earl Holley Application June 24, 1940, Serial No. 342,095

1 Claim.

.The object of this invention is to improve the fuel mixing device illustrated in the Peltz Patent 1,665,145. In that device the pressure difference between" that in the air entrance to'the carburetor and the pressure in the venturi throat, also located in the air entrance, is used to control the fuel flow across a fixed orifice and to thereby maintain a fixed fuel air ratio. The fuel is delivered on the downstream side of the throttle. This feature of delivering'fuel on the engine side of the throttle is, of course, of paramount importance today in aircraft; as all attempts to deliver fuel 9n the atmospheric side of the throttle as in ordinary auto'mobile type carburetors, I

have resulted in disastrous crashes, due to freezing not only on the throttle, but in the air passage immediately adjacent to and on the engine side of the throttle valve.

In the airplane it is also necessary to provide some means for correcting for extreme changes in air density. Furthermore, it is desirable .to modify and adapt the Peltz principle to the ordinary airplane carburetors now in general use.

In the drawings:

Figure 1 shows the application of the Peltz principle to an airplane carburetor having an altitude correcting device.

Figure 2 is a modification of the Peltz device in which the venturi is placed on the engine side of the throttle valve.

Figure 3 showsthe application .of the Peltz principle to a well known variable venturi carburetor which has come into general use in the air.

Figure 4 shows the application of theprlnciple to an updraft carburetor with an anterior throttle.

' In Figure 1, I0. is the fuel entrance; II is the needle valve controlled by the diaphragm l2; l3 and 14 are the compression springs which maintain a definite pressure on the diaphragm ber with the air entrance 21, that is, with the 'piezometer ring 33 located in the main air entrance. The fiow through 26 is controlled by the throttle 28. After the air passes the throttle 28, it passes the fuel outlet 29 which is spring loaded in order to provide a small amount of spraying in the air passage 3|) which leads to the supercharger of the airplane engine. The float 3| is located in the upper portion of the chamber l5 and permits vapor to escape from this chamher through the pipe 32 which can discharge into,

the air entrance, or can be returned to the fuel pump.

In Figure 2 the throttle 28 is located in the air entrance and the throat of the venturi 26 is con- I2 and therefore maintain a definite pressure in the fuel entrance chamber l5; I6 is the fuel outlet chamber. which communicates with the fuel entrance chamber through a restricted orifice I! controlled by the barometric device I8, which. automatically restricts the fuel flow at high altitudes. The chamberlB has a fuel outlet I 9 controlled by a valve 20 which is controlled.

by the diaphragm 2| through a link 22. Obviously the flow past l8 and through the orifice I1 is determined by.the pressure difference between the chamber l5 andthe chamber I 6.

The compression springs l3 and I4 press against each other through the rod 23 which slides freely through the partition 9 which forms nected as before with the chamber 24. The chamber 25 now communicates with the piezome ter ring 33 located on the engine side of the throttle 28 and of the venturi 26 and far enough away from the throttle 28 so that the disturbances created by the throttle have died down, so that a true reading can be obtained and so that the pressure difference between that in the piezometer ring 33 and the pressure in the throat of the venturi 26 truthfully reflects the air flow and accurately determines fuel flow.-

As before the fuel discharges through a spring loaded valve 29 into the mixture entrance 30 leading to the supercharger (not shown), and as before the floatvalve 3| in the upper portion of the chamber l5 allows any vapor in that chamber to escape through a passage 32 which communicates with the air entrance. The ad- In Figure 3 a variable venturi is shown correspending to acarburetor in general use, so thata few necessary modifications must be introduced. The variable Venturi throttles 34 and 35 are connected together by gears 36 and 31 shown in broken lines. A series of orifices, one of which is shown at 38, permits sub-atmosphericpressure existing in the throat of the variable venturi to -influence the pressure in the chamber 24. In-

stead of the compression springs I3- and I4, two

- tension springs 39 and 49 connect the two diaphragms I2 and 2| together by means of a wire rod guided in ,the partition 40. The piezometer ring 33 is located on the engine side of the variable venturi and the fuel which discharges from the fuel chamber I6 flows through the pipe I9 7 into a chamber 4| located in a hollow stream lined bridge 42 which forms the central'portion of the rectangular variable venturi. The fuel issues through openings 43 and 44 and entrained with it is a small quantity of air admitted through the opening 45.

Although it is no partof this invention, 1 have also shown the means for adding the extra fuel needed to prevent the ordinary air cooled airplane engine overheating (90% of airplane engines in use today are air cooled). These means consist of the fuel entrance 46 in which is located a fuel venturi 41, the differential pressures of which are used to move the diaphragm 48 and to open a needle valve 49 against the spring 50, and thus admit fuel to the passage 5|, to which passage air' is admitted through the into the ring 33 when the float 3| is off its seat.

The piezometer ring 33, at all times, communicates freely with the chamber 25 at the left hand side of the diaphragm I2, so that there is at all times a pressure difference between the chambers 24- and 25 responsive to air flow throughthe variable venturi causing --a flow through the orifice ll of the fuel in proportion to the air flow.

In Figure 4, an air entrance 60 is controlled by a throttle 6| and a manually operated lever 62 which is connected to-the throttle lever 94 by a spring 63. The lever 65 pivoted on the pin 99 is connected to a rod 95 which engages with the lever .65 through a shoulder 64 on the rod 95, when the lever 62 is in the extreme closed position. After the throttle 6| is closed to the position determined by the stop 96, the manually operated lever 62 may be moved clockwise as far as the spring-63 will permit. During this movement, after the throttle BI is closed to its idling position, the head 64 of the rod 95 engages with the lever 65 pivoted at '99 which is turned clockwise, the roller 66 is released from the shoulder 98 of the lever 65, and the spring 61 causes the diaphragm I4 to move down carrying with it the lever 68, and with it the valve 69 which positively shuts off the fuel. Thus, when the manually operated throttle lever 62 is moved clockwise into the position at which the engine is required to stop, the fuel is positively cut oil and the danger of leakage, etc., eliminated. This device is therefore a safety, device to prevent loss of fuel and the resultant fire hazthe barometric device I8 and flows then into the chamber I6 where the pressurecreated in the chamber I6 acts against the diaphragm 2| so as to cause the valve 20 to open and reduce the pressure in the chamber I6 below that in I5. This reduction in pressure corresponds to and is balanced by the difference between the pressure in the piezometer ring 33 and the pressure in the throat of the variable venturi when the throttle is wide open. Obviously this device would give rich mixture at closed throttle position and vice versa. When the throttle is in the intermediate position, as shown, a needle valve 54 operated by the lever I98 connected to the throttle 34 modifies the suction in the chamber 24 by admitting air at a relatively high pressure from the piezometer ring 33 through the passage I99. The pressure in 33 is necessarily higher than the pressure in the variable venturi where the velocity is at a maximum and the pressure is at a minimum. A restriction determines the effect of the air admitted past the needle valve 54. A passage II'II permits free communication between the chamber 25 and the ring 33. In other words, at every position of the throttle, the pressure in the chamber 24 will be intermediate the pressure in the throat of the variable venturi and the pressure in the piezometer ring 33 on the downstream side of the variable venturi and the only time the device will function exactly as the device functions in Figures 1 'and 2 and in the Peltz Patent 1,665,145, is when the throttle is wide open and the needle valve 54 closesthe passagewayinwhich it slides and prevents the piezometer ring 33 communicating with the chamber 24. The arm I08 is made adjustable relative to the throttle valve 34. The vapor escapes through the passage I II ardwhen a plane is re-started after standing still, with the engine stopped. 'When the throttle is first opened the reverse turn takes place,

the rod 95 moving to the left, the lever moving clockwise under the influence of the spring, the I roller 66 being raised slightly by the shoulder 98, the lever 68 being raised slightly, and the valve 69 being raised slightly so as to admit a small quantity of fuel so that the engine can idle. The moment the enginepicks up speed and the throttle 6| is opened, the depression in the Venturi throat causes the diaphragm to move and regulate the fuel flow according to the Peltz principle referred to.

The venturi throat II is provided with a hollow passage I2 known in the industry as a piezometer ring which is connected with the air chamber I3 which is bounded on its lower side by the flexible diaphragm I4. Below the diaphragm I4 is the outlet fuel chamber I5 which is supplied with fuel through the opening 16 controlled by the needle 11 which is barometrically controlled by the three aneroid elements I8.

The fuel inlet chamber I9 is bounded on its lower face by the diaphragm which is supported by the spring 8| which is stiff enough to create a pressure in the chamber 19 equal to the pressure created in the chamber I5 due to the stiffness of the spring 61. The chamber 82 which contains the spring 8| is in communication through the passage 83 with the air entrance 60 on the engine side of the throttle 6|.

' Th opening 83 is suflicientiy restricted so that is connected by the link 85 to-the lever 94 and so to the throttle 6| so that every time the throttle is opened, air is compressed in the pump 84 l and discharges through the passage 86 into the chamber 82.

The ordinary diaphragm operated mechanism 87 with needle 88 is provided to regulate chamber 19 and the vapor discharges through the pipe 92 into the mixture outlet 93.

I Operation The operation follows closely that described in the Peltz Patent 1,665,145 above referred to. When the throttle is closed, or when the barometer falls in the case of Figures 2 and 3, and in the case of Figure 1 when the barometer pressure falls, the pressure in the fuel chamber l fails a corresponding amount. Although the pressurein the chamber l5 may be, and will be in the construction shown in Figure 1, at all times higher than atmospheric pressure, the barometric device I8 will respond aswell to variations above atmospheric pressure as it will to variations in pressure below atmospheric pressure, and when the pressure in the air entrance 2'! falls, .the pressure in the fuel chamber I 5 falls to a like degree. For example, the pressure in l5, Figure 1; falls from say 17 lbs. to lbs. per square inch absolute. In the case of Figure 2,

when the throttle 28 is closed and in Figure 3 when the two throttles 34 and 35 are closed, the pressure in the air chamber 25 fails because the pressure in the ring 33 falls. Therefore, the pressure of the liquid in the chamber l5 also falls. The .barometric element l8 then expands and restricts the opening H, in order to maintain the fuel ratio constant to compensate for the fall in air density.

The device shown in Figure 3 can be made to hold the basic fuel-air ratio constant. At wide open throttle when the valve 54 obstructs the passage between the annular chamber 33 and the chamber 24, the device functions as the device shown in Figures 1 and 2. At part throttle the needle valve 54 can be set, either by changing the taper on the needle or by'moving the arm .98 relative to the throttle 34, to modify the effect of the pressure difference between the Venturi throat suction and the Venturi outlet suction,

so as to prevent the excessive suction at part throttle producing excessively rich mixture.

In the construction shown in Figure 3, there is a slight leakage of fuel past the wire connecting the two tension springs 39 and 48. This will be corrected by the taper of the needle regulating the orifice H.

The fuel needed to prevent'the engine overheating can be furnished in the ordinary manner by the opening of the fuel needle 49. This last mentioned feature, of course, is no part of this invention. It is illustrated merely to show the adaptability of the Peltz principle to the device now in general use.

- What I claim is:'

-A carburetor having an air entrance, a throttling means therein forming variable Venturi mixing chamber, a? fuel entrance chamber, a fuel exit chamber,- a restricted passage therebetween, means for maintaining a definite pressure difference in said fuel chambers at every 'air flow and at each position of the throttling means comprising a passage connecting the throat of aid variable Venturi with an air chamber controlling the pressure in said fuel exit chamberya passage connecting the mixture outlet with an air chamber adapted to control the pressure in the fuel entrance chamber, valve means controlled by the throttle for reducing the eiTect of the difference between the air pressure on the engine side of the variable Venturi and the pressure in the throat of the variable Venturi when the' variable Venturi throttle is in a partly closed position, said fuel chambers each having a flexible wall, said flexible walls forming one wall of each air chamber, a fuel entrance valve in said fuel entrance chamber adapted to be opened by an increase in air pressure acting on the flexible wall of said fuel entrance chamher, a fuel exit valve in said fuel exit chamber adapted to be opened by a decrease'in air pressure acting on the'flexible wall of-said fuel exit chamber.

' STANLEY M. UDALE. 

